The haircut sometimes known as The Hitler Youth or The Michael Pitt/Jimmy Darmody/Boardwalk Empire or The Undercut has officially hit the mainstream: Biggest Loser fitness guru Bob Harper was spotted sporting very short sides and a long, floppy top on Rachael Ray Wednesday.

While Harper has had this 'do for some time, this looks like the shortest his hair has ever been on the sides. Many stars have been rocking what we could call an Extreme Hitler Youth (but let's not) for some time, though Brad Pitt really classed it up when he debuted his haircut at the Academy Awards in March. Before Pitt, David Beckham, the aforementioned Michael Pitt, Miguel and Justin Timberlake were seen with versions of the look. Recently Adam Levine has been spotted with it, except this time he's made it super hype by shaving just one side of his head, while the other remains just short.

This new version of the haircut is a little different because instead of slightly shorter sides, men are now getting the sides and back of their heads legitimately buzzed, while still allowing the top to flop down (artfully, of course). Others choose to carefully gel that swatch back. The variance between the hair on the top of the head is now more severe, but is still not truly punk like a mohawk. It's basically just a version of the hi-top fade for men whose hair doesn't naturally lend itself to standing straight up.

While the recent popularity of this hairstyle in some form or another has been kicking around for a couple years now (there are numerous YouTube tutorials devoted to helping men style the look and/or get the haircut themselves), I knew it was big amongst mere mortals when I noticed it on a male friend last week. This is a man who is sartorially inclined but definitely not high maintenance about his look, but here he was, with hair that was long and floppy on top but very short on the sides. When I asked him why he'd gone for this haircut, he said, "I had a Groupon for a fancy salon and I asked them to give me something I wouldn't have to do anything to. This is what they did."

Whatever you want to call it, this haircut at first seems like it takes a lot of work, but upon further consideration, it probably does grow out pretty well. Once you have the wheels set in motion, you can grow out the sides until you're ready for some sharp contrast again. It even has a potential great catchphrase: "Extreme Hitler Youth: If you want, it can just be a phase." (Sorry, I forgot, we're not calling it that.)